Pen injectors are known in the prior art and typically include a pen needle for insertion into a patient to allow proper drug administration. Such pens may be disposable, containing a single dose of a drug, or reusable, containing a single dose or more of a drug. The pen needle includes a double-ended needle with a distal end formed for insertion into a patient and a proximal end formed for insertion into a drug vial or cartridge located inside a pen injector body. The pen needle should be single-use and replaced with each administered dose.
Safety pen needle assemblies have been developed in the prior art which shield a pen needle after use. Typically, with this arrangement, after an injection, a lock mechanism locks a shield over the patient end of a safety pen needle and prevents reusage. The lock mechanisms of current safety pen needle assemblies implicate various considerations, including cost and manufacturing. Reliability is highly desired.